安卓AndroidStudio实现计算器

叁歲伎倆 2022-03-07 07:48 442阅读 0赞

### **一、内容**： ###

基于AndroidStudio，实现一个简易的计算器（界面+简单的计算）。

下图是整体界面：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70][]

### 二、思路 ###

1.  **首先设计界面，activity\_main.xml**

计算器界面，需要：文本框TextView——显示数字；数字、符号按钮Button

<?xml version="1.0" encoding="utf-8"?>
    <GridLayout  xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:rowCount="6"
        android:columnCount="4"
        >
        
        <TextView
            android:id="@+id/text"
            android:layout_width="350dp"
            android:layout_height="wrap_content"
            android:layout_columnSpan="4"
            android:layout_marginLeft="4px"
            android:gravity="left"
            android:textSize="50dp" />
    
        <Button
            android:id="@+id/btnClear"
            android:layout_width="353dp"
            android:layout_height="wrap_content"
            android:layout_columnSpan="4"
            android:background="@color/colorAccent"
            android:text="清除"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn1"
            android:text="1"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn2"
            android:text="2"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn3"
            android:text="3"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnPlus"
            android:background="@color/colorPrimary"
            android:text="+"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn4"
            android:text="4"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn5"
            android:text="5"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn6"
            android:text="6"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnSubtract"
            android:background="@color/colorPrimary"
            android:text="-"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn7"
            android:text="7"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn8"
            android:text="8"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn9"
            android:text="9"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnMultiply"
            android:background="@color/colorPrimary"
            android:text="*"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnPoint"
            android:text="."
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btn0"
            android:text="0"
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnSum"
            android:text="="
            android:textSize="26sp" />
    
        <Button
            android:id="@+id/btnDivide"
            android:background="@color/colorPrimary"
            android:text="/"
            android:textSize="26sp" />
    </GridLayout>

**2.接下来是功能的实现，MainActivity.java**

给各个按钮注册点击事件、对输入内容的判断和计算等。

package com.example.asus.calculator;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.widget.Button;
    import android.widget.TextView;
    import android.view.View;
    import android.view.View.OnClickListener;
    
    public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    
        Button btn0,btn1,btn2,btn3,btn4,btn5,btn6,btn7,btn8,btn9,
                btnClear,btnPlus,btnSubtract,btnMultiply,btnDivide,btnSum,btnPoint;
        TextView text;
        String str = "";
        boolean clr_flag;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            btn0 = (Button) findViewById(R.id.btn0);
            btn1 = (Button) findViewById(R.id.btn1);
            btn2 = (Button) findViewById(R.id.btn2);
            btn3 = (Button) findViewById(R.id.btn3);
            btn4 = (Button) findViewById(R.id.btn4);
            btn5 = (Button) findViewById(R.id.btn5);
            btn6 = (Button) findViewById(R.id.btn6);
            btn7 = (Button) findViewById(R.id.btn7);
            btn8 = (Button) findViewById(R.id.btn8);
            btn9 = (Button) findViewById(R.id.btn9);
            btnClear = (Button) findViewById(R.id.btnClear);
            btnPlus = (Button) findViewById(R.id.btnPlus);
            btnSubtract = (Button) findViewById(R.id.btnSubtract);
            btnMultiply = (Button) findViewById(R.id.btnMultiply);
            btnDivide = (Button) findViewById(R.id.btnDivide);
            btnPoint = (Button) findViewById(R.id.btnPoint);
            btnSum = (Button) findViewById(R.id.btnSum);
    
            text = (TextView) findViewById(R.id.text) ;
    
            btn0.setOnClickListener(this);
            btn1.setOnClickListener(this);
            btn2.setOnClickListener(this);
            btn3.setOnClickListener(this);
            btn4.setOnClickListener(this);
            btn5.setOnClickListener(this);
            btn6.setOnClickListener(this);
            btn7.setOnClickListener(this);
            btn8.setOnClickListener(this);
            btn9.setOnClickListener(this);
            btnClear.setOnClickListener(this);
            btnPlus.setOnClickListener(this);
            btnSubtract.setOnClickListener(this);
            btnMultiply.setOnClickListener(this);
            btnDivide.setOnClickListener(this);
            btnPoint.setOnClickListener(this);
            btnSum.setOnClickListener(new click());
    
        }
    
        public void onClick(View v) {
            String input=text.getText().toString();
            switch (v.getId()){
                case   R.id.btn0:
                case   R.id.btn1:
                case   R.id.btn2:
                case   R.id.btn3:
                case   R.id.btn4:
                case   R.id.btn5:
                case   R.id.btn6:
                case   R.id.btn7:
                case   R.id.btn8:
                case   R.id.btn9:
                case   R.id.btnPoint:
                    if(clr_flag){
                        clr_flag=false;
                        str="";
                        text.setText("");
                    }
                    text.setText(input+((Button)v).getText());
                    break;
                case R.id.btnPlus:
                case R.id.btnSubtract:
                case R.id.btnMultiply:
                case R.id.btnDivide:
                    if(clr_flag){
                        clr_flag=false;
                        input="";
                        text.setText("");
                    }
                    text.setText(input + " " + ((Button)v).getText() + " ");
                    break;
                case R.id.btnClear:
                    text.setText("");
                    break;
            }
        }
        class click implements OnClickListener{
            public void onClick (View v) {
                getResult();//调用方法，计算结果
            }
        }
    
        private void getResult () {
            String str1 = text.getText().toString();
            if(str1 == null || str1.equals("")){
                return;
            }
            if(!str1.contains(" ")){
                return ;
            }
            if(clr_flag){
                clr_flag=false;
                return;
            }
            clr_flag=true;
            double result = 0;
    //        运算符前的数字
            String s1 = str1.substring(0,str1.indexOf(" "));
    //        运算符
            String op = str1.substring(str1.indexOf(" ")+1,str1.indexOf(" ")+2);
    //        运算符后的数字
            String s2 = str1.substring(str1.indexOf(" ")+3);
    //        判断
    //        1. 如果s1、s2都不为空
            if(!s1.equals("")&&!s2.equals("")) {   //包含小数点运算
                double d1 = Double.parseDouble(s1);//则数字都是double类型
                double d2 = Double.parseDouble(s2);
                if (op.equals("+")) {   //如果是 +
                    result = d1 + d2;
                } else if (op.equals("-")) {   //如果是 -
                    result = d1 - d2;
                } else if (op.equals("*")) {   //如果是 *
                    result = d1 * d2;
                } else if (op.equals("/")) {   //如果是 /
                    if (d2 == 0) { //如果被除数是0
                        result = 0; //则结果是0
                    }
                    else {//否则执行正常是除法运算
                        result = d1 / d2;
                    }
                }
                if (!s1.contains(".") && !s2.contains(".") && !op.equals("/")) {//如果是整数类型
                    int r = (int) result; //都是整形
                    text.setText(str1 + " = " + r + "");
                } else{
                    text.setText(str1 + " = " + result + "");
                }
            }
    //            如果s1不是空，s2是空
            else if(!s1.equals("")&&s2.equals("")){
                double d1 = Double.parseDouble(s1);
                if (op.equals("+")){
                    result = d1;
                }
                if (op.equals("-")) {
                    result = d1;
                }
                if (op.equals("*")) {
                    result = 0;
                }
                if (op.equals("/")) {
                    result = 0;
                }
                if(!s1.contains(".")) {
                    int res = (int) result;
                    text.setText(str1 + " = " + res+"");
                }else {
                    text.setText(str1 + " = " + result+"");
                }
            }
    //        如果s1是空，s2不是空
            else if(s1.equals("")&& !s2.equals("")){
                double d2 = Double.parseDouble(s2);
                if(op.equals("+")){
                    result = 0+d2;
                }else if(op.equals("-")){
                    result = 0-d2;
                }else if(op.equals("*")){
                    result = 0;
                }else if(op.equals("/")){
                    result = 0;
                }
                if(!s1.contains(".") && !s2.contains(".")){
                    int res = (int) result;
                    text.setText(str1 + " = " + res + "");
                }else{
                    text.setText(str1 + " = " + result + "");
                }
            }else{
                text.setText("");
            }
        }
    }

### 三、效果展示 ###

1.加法：从左到右，分别为包括①小数点运算、②运算符前不为空，后为空、③运算符前为空，后不为空三种情况，均能实现运算。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 1][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 2][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 3][]

2.减法：从左到右，分别为包括①小数点运算、②运算符前不为空，后为空、③运算符前为空，后不为空三种情况，均能实现运算。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 4][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 5][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 6][]

3.乘法：从左到右，分别为包括①小数点运算、②运算符前不为空，后为空、③运算符前为空，后不为空三种情况，均能实现运算。（注：字符串为空，则认为是0）

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 7][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 8][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 9][]

4.除法：从左到右，分别为包括①小数点运算、②运算符前不为空，后为空、③运算符前为空，后不为空三种情况，均能实现运算。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 10][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 11][]   ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDE0MTQ3Mw_size_16_color_FFFFFF_t_70 12][]

### 四、总结 ###

在计算器的案例中，页面设计、布局等都是很基础的知识，主要要解决的问题在于对输入内容的分割，以及对分割后的字符的逻辑运算。作为一个简易的计算器，我只实现了简单的单个运算符的运算。更精细的计算器，可以通过队列和栈实现运算优先级，即包括”(“、”)”，以及多个运算符共同计算的功能。

只有自己真正完成过项目，才能明白平时使用的这些APP，都是设计者们花费了多大的心思才能一步步完善，最后呈现在我们眼前的。向每一位程序员们致敬！

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